As to an acid generator to be used for a photoresist composition, JP2006-257078A1 mentions a salt represented by the following formula.

JP2007-224008A1 mentions a salt represented by one of the following formulae.

JP2013-41257A1 mentions a salt which consists of an organic action having no acid-labile group and no nitrogen atom as well as a anion represented by one of the following formulae.

(Lb1 represents a divalent organic group, and Xb1 represents an acid-labile group having no nitrogen atom.)
JP2012-97074A1 mentions a salt represented by the following formula.

(L1 represents a divalent C1 to C17 saturated hydrocarbon group or the like, W represents a divalent C3 to C36 alicyclic hydrocarbon group or the like, and Xb1 represents a fluorine atom or a C1 to C6 fluorine-containing alkyl group.)